This invention relates to an improved dental pulp capping and cavity lining composition and its method of preparation. The beneficial effect of calcium hydroxide on tooth pulp and secondary dentine formation has been well known in dentistry for many decades. The original calcium hydroxide suspensions were later mostly replaced by hard setting calcium hydroxide formulations.
Three prior art disclosures for which United States Patents were subsequently granted have special relevance to the present invention. U.S. Pat. No. 2,516,438 advocates that a mixture of excess calcium hydroxide and eugenol be used as pulp capping material. This was prior to the advent of polymerizable, acrylic functional, dental restorative materials, the setting of which is unfortunately inhibited by compositions containing eugenol, all of which contain some residual free eugenol even after many years. It is reported in the Science of Dental Materials (R. W. Phillips) 1973, Chapter 7, page 93, that as much as 5 percent free eugenol, from an original eugenol content of 16.4 percent, may be present in a zinc oxide and eugenol mixture, even ten years after mixing, and a similar finding would be expected in the case of calcium hydroxide and eugenol.
Since the presence of excess available free calcium hydroxide has been found beneficial in the stimulation of reparative secondary dentin formation over exposed dental pulps, U.S. Pat. No. 3,047,400 advocated the continued use of calcium hydroxide, but now reacted with non-eugenol phenolic derivative, to achieve compatibility with the newly introduced, unfilled acrylic restorative materials.
After 1965, filled acrylic functional resin based composite restoratives were introduced and rapidly gained wide acceptance. Concurrent with this development the use of the acid-etched enamel bonding technique also gained very wide acceptance, creating a need for pulp capping and cavity lining materials to be acid resistant. U.S. Pat. No. 4,080,212, places major emphasis on the prime objective stated as "the prevention of discoloration", even foregoing all the inherent advantages of a two paste system in order to achieve this objective.
Accordingly, it is an object of this invention to provide a dental pulp capping composition which when placed over moderately inflamed dental pulp will reduce inflammation and induce dentinal bridge formation thus increasing the probability of pulp healing.
It is also an object of this invention to provide a dental cement composition capable of fast curing in an oral environment and having high crushing strength to resist amalgam condensation pressure.
It is another object of this invention to provide a pulp capping and cavity lining material which is resistant to the type and concentration of acids used for etching tooth enamel and which also exhibits complete compatibility with composite restorative materials.
It is a further object of the present invention to provide a novel capping and cavity liner material in the form of a two paste system.